import 'package:path/path.dart' as path;

import '../../api/model/downloader_config.dart';

/// Reads the downloader config, applies first-launch defaults and persists
/// the result when the init changed it. Persisting is skipped when the
/// initial load failed: writing defaults over an unreadable store would
/// wipe the user's configuration.
Future<DownloaderConfig> loadDownloaderConfig({
  required Future<DownloaderConfig> Function() load,
  required Future<void> Function(DownloaderConfig config) save,
  required Future<String> Function() defaultDownloadDir,
  void Function(Object error, StackTrace stackTrace)? onLoadError,
  void Function(Object error, StackTrace stackTrace)? onSaveError,
}) async {
  DownloaderConfig config;
  var loaded = true;
  try {
    config = await load();
  } catch (error, stackTrace) {
    onLoadError?.call(error, stackTrace);
    config = DownloaderConfig();
    loaded = false;
  }
  final changed = await initDownloaderConfig(config, defaultDownloadDir: defaultDownloadDir);
  if (loaded && changed) {
    // Persist the seeded categories so the backend can route
    // downloads to them right away instead of waiting for the settings page
    // to save the config.
    try {
      await save(config);
    } catch (error, stackTrace) {
      onSaveError?.call(error, stackTrace);
    }
  }
  return config;
}

/// Applies defaults to a freshly loaded config: theme/tracker/proxy basics,
/// the default download directory, and seeding the built-in categories when
/// nothing exists yet. Returns whether the config changed and should be
/// persisted.
Future<bool> initDownloaderConfig(
  DownloaderConfig config, {
  required Future<String> Function() defaultDownloadDir,
}) async {
  var changed = false;
  final extra = config.extra;
  if (extra.themeMode.isEmpty) {
    extra.themeMode = 'system';
  }
  if (extra.themeColor.isEmpty) {
    extra.themeColor = 'green';
  }
  if (config.proxy.scheme.isEmpty) {
    config.proxy.scheme = 'http';
  }
  if (config.downloadDir.isEmpty) {
    final downloadDir = await defaultDownloadDir();
    // An unknown directory stays empty, the backend resolves its own.
    if (downloadDir.isNotEmpty) {
      config.downloadDir = downloadDir;
      changed = true;
    }
  }
  if (config.categories.isEmpty && config.downloadDir.isNotEmpty) {
    config.categories = [
      _builtinCategory('categoryMusic', path.join(config.downloadDir, 'Music')),
      _builtinCategory('categoryVideo', path.join(config.downloadDir, 'Video')),
      _builtinCategory('categoryDocument', path.join(config.downloadDir, 'Document')),
      _builtinCategory('categoryProgram', path.join(config.downloadDir, 'Program')),
    ];
    changed = true;
  }
  if (config.githubMirror.mirrors.isEmpty) {
    config.githubMirror.mirrors = [
      GithubMirror(type: GithubMirrorType.jsdelivr, url: 'https://fastly.jsdelivr.net/gh', isBuiltIn: true),
      GithubMirror(type: GithubMirrorType.ghProxy, url: 'https://fastgit.cc', isBuiltIn: true),
    ];
  }
  return changed;
}

DownloadCategory _builtinCategory(String nameKey, String categoryPath) {
  return DownloadCategory(
    name: '',
    path: categoryPath,
    isBuiltIn: true,
    nameKey: nameKey,
    extensions: List<String>.from(kDefaultCategoryExtensions[nameKey] ?? const []),
  );
}